1. Field of the Invention
The invention generally relates to antenna systems and, more particularly, the invention relates to a reconfigurable antenna.
2. Description of the Related Art
The detection, location, identification, and characterization of electromagnetic (EM) signals of types that have a low probability of intercept is an increasingly challenging problem. In general, EM signals with a low probability of intercept are transmitted by adversarial sources and thus employ various methods to reduce their signature. Such methods include frequency hopping, multiple signal polarizations, and spread spectrum encoding techniques. In addition, the locations of the sources of such signals are not fixed and may change quite rapidly. The number of sources or EM signals that need to be located and tracked may also change depending on the particular circumstances.
A broadband antenna is generally required in order to track such EM signals. Frequency independent antennas such as spirals and quasi frequency independent antennas such as log periodic antennas are quite large and their use in antenna array is quite limited. Also, an adaptive array using such broadband elements would require a feed structure integrated to a true time delay network in order to achieve multiple beams and beam scanning. Such feed networks are difficult to design and are expensive to implement.
Therefore, there exists a need in the art for a reconfigurable antenna capable of dynamic reconfiguration of operating frequency, polarization, bandwidth, number of beams and their spatial directions, and radiation pattern shape without the need for a complex feed network.
The disadvantages associated with the prior art are overcome by a reconfigurable antenna capable of dynamic reconfigurability of several antenna parameters. Specifically, the present invention is an antenna comprising a plurality of surface PIN (SPIN) devices arranged in a gridlike array. Each of the SPIN devices in the array can be individually activated or deactivated. When a SPIN device is activated, the surface of the device is injected with carriers such that a plasma is produced within an intrinsic region of the SPIN device. The plasma is sufficiently conductive to produce conductor or metal-like characteristic at the surface of the device. Various ones of the SPIN devices in a SPIN device array can be activated to electronically xe2x80x9cpaintxe2x80x9d a conductive pattern upon the substrate supporting the SPIN devices. Through selective activation of the SPIN devices, various surface antenna patterns can be produced upon the substrate including dipoles, cross dipoles, loop antennas, Yagi-Uda type antennas, log periodic antennas, and the like.
Additionally, the SPIN device array may be selectively activated to produce holographic antennas. In a holographic antenna, the SPIN devices are activated to produce a holographic metallization pattern. The pattern is excited by a surface RF wave transmitted onto the substrate from a surface mounted radiator such as a surface mounted dipole antenna. The surface wave excites a particular antenna pattern depending upon the shape of the pattern produced by the activated SPIN devices. Changing the pattern of the SPIN devices results in beam steering of the antenna radiation pattern.